Almost all "alternative" browsers are Chromium based or Gecko/Firefox based. If there are any that are truly scratch-built other than the text-based browsers such as lynx or w3m I'd be interested to hear about them. I'd guess they are extremely limited in features.

Not the commenter you're replying to, but I've been using LibreWolf for the last few months.

It's a bit more privacy focused, so may need some tweaking to your liking (by default it won't persist history, zoom levels, cookies, etc.)

LibreWolf, Iron Fox, and Brave are all worth a look, I think.